Download Forman - Chandra X

X-ray Bright, Optically Normal Galaxies - XBONGS
Forman, Anderson, Hickox,
Jones, Murray, Vikhlinin, Kenter
and the Bootes Team
Bootes Survey
9.3 sq. degrees with Chandra
4632 X-ray sources
1600 optical spectra
NOAO Deep Wide Field Survey
AGES Optical Spectroscopic Survey
20,000 galaxy spectra
Key to success is contiguous area and
efficient spectroscopy with Hectospec
XBONGS - debated nature since Einstein Obs. (Elvis et al. 1981)
Dilution of optical AGN signature by galaxy light
Absorption
Radiatively inefficient accretion flow (little optical/UV)
The XBootes Survey
• 126 ACIS 5 ksec pointings
• Joint GTO (Murray) and GO (Jones)
program
• 14h 32m +34 06’
• 4642 sources detected (>=2 cts)
– 625 spurious
• 3293 sources detected (>=4 cts)
– 22 spurious
• 42 extended sources (>=10 cts)
• fmin= 4(8)x10-15 erg cm-2 s-1 (0.5-7 keV)
• 98% sources 4 cts matched to NDWFS
candidates (R26)
Murray et al. ApJ S 163, 2005
Kenter et al. ApJ S 163, 2005
Brand et al. ApJ, 2006
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Spectroscopy in Bootes
• MMT/Hectospec fiber spectrograph
– 300 fibers
– 6 A resolution, 4000-8000A
• Spectroscopy
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Complete X-ray >4 cts and I<21.5 and galaxies I<19.5
1,531 X-ray selected and ~19,000 galaxies
1175 Broad Line Galaxies
50 Narrow Line Galaxies
– 258 XBONGS
• Huge sample
• 17% of total
• 0<z<1
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Heterogeneous Class of Objects
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From optical SED’s and
morphology
Red Ellipticals 60
Blue Ellipticals 84
Interacting
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Spirals
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“AGN”
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(Fioc &Rocca-Volmerange
1997; Francis et al. 1991)
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Redshift Distribution
XBONGS
Broad line AGN
Narrow line AGN
XBONGS and NL AGN
same distribution
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XBONG Magnitude Distribution
XBONG
BL (z<1)
NL
XBONG counterparts similar to NL/BL AGN
possibly somewhat fainter than NL AGN
Argues against significant dilution of lines by
underlying host galaxy for all of sample
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Luminosity Distributions
•200 XBONGs with Lx>1042 erg/s
•50% with Lx>1043 erg/s
•XBONG’s and NL AGN
•Similar Lx
•Similar Fx/FR
•Argues against dilution for all of
sample
XBONG
BL (z<1)
NL
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Merged X-ray Spectra
Type
Red Ellipticals
Blue Ellipticals
“AGN”
Interacting
 (90% error) and no absorption
1.12-1.32
1.55-1.73
1.83-2.25
1.28-1.56
(confirmed by hardness ratios)
Red ellipticals - for an assumed =1.9 power law
nH ~ 0.7-1.1 x 10 22 cm-2 (90% confidence)
• Some “types” absorbed, some not absorbed
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IRAC Color-Color Diagrams (following Stern et al.)
BL AGN
Z<0.15
XBONGS
BL AGN
NL AGN
0.45<Z<0.60
0.60<Z<0.75
0.15<Z<0.30
Red Blue
0.30<Z<0.45
0.75<Z<1.00
z<0.3 Dilution - about 30%; consistent with Georgantopoulos et al.
dilution criterion
z>0.3 XBONGS concentrated under AGN wedge
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Radiatively Inefficient Accretion Flows (RIAF)
•At low accretion rates (Yuan & Narayan)
- Optically thick disk is truncated at Rtrans
- Interior to Rtrans flow is RIAF (radiatively inefficient;
optically thin)
- Observed in high state galactic black holes
-X-rays from inverse Compton in RIAF
-Little optical or UV since no disk at small radii
- model requires L/Ledd < 0.03
•Test RIAF model with spheroidal sample of XBONGS
-Use optical luminosity as proxy for MBH (108-109 Msun)
- MBH yields Ledd
-Derive AGN LBOL from SED (Elvis et al.)
- For 46 XBONGS, LBOL /Ledd < 0.01
VIABLE MODEL - needs detailed SED’s
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Conclusions
• Large XBONG sample
– 258 with redshifts to 1
– Variety of optical morphologies
• Origin of XBONG signature
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Some dilution at low z (small fx/fR)
Some absorption - esp. red ellipticals with nH~1022 cm-2
Many sources show little (<1022 cm-2) absorption
RIAF (radiatively inefficient accretion flow)
• Spheroidal sample has low Eddington ratio (Lbol/Ledd<0.01)
– Probably some BL Lac’s
XBONG’s are a heterogeneous class
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• Deeper & Wider
Future Work
– Chandra and XMM-Newton
– Larger samples, better S/N
• X-ray spectra
– Better models applied to ensemble of spectra
• Optical spectra for fainter sources
– Probe to higher z
• Detailed analysis of optical spectra
– Derive equivalent widths and line strength limits
– Model NL galaxies, compare to XBONGS
• Derive SED’s for different classes to test e.g., RIAF models
• Study local environment
– 20,000 galaxy redshifts
– Measure local density, compare to other AGN classes
Remarkable class
Promises new insights into accretion process
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MMT Bootes survey
Optical spectroscopy: AGES survey w/ MMT/Hectospec
The first sample contains ~1000 broad line AGNs, 80 narrow-line AGNs, and 27,000
“normal” galaxies.
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